The art includes a Five-Byte Packet (FBP) procedure for compressing electronic signatures. The FBP procedure stores signature data such as LineTos and MoveTos, as well as other specific data about the hardware touch pad such as whether the pen is UP or DOWN. A signature is a collection of such five-byte packets representing (absolute or relative) movements.
Notably, the FBP procedure does not compress data.
(A “LineTo” is a movement with the pen down. A LineTo draws a line of a signature. A “MoveTo” is a movement with the pen up. No signature line results from a MoveTo.)
The art also includes a word-signature (SIG) format. Like the FBP format, the SIG format stores MoveTos and LineTos in order to reconstruct a signature. SIG stores movements as absolute data and, in contrast to the FBP format, compresses the resulting data. The SIG format does not store hardware status.
SIG is a four-byte format. Two bytes store the X (horizontal) MoveTo or LineTo data. An additional two bytes store the corresponding Y data.
Pen-status data is encoded as predetermined special MoveTo/LineTo data to indicate a PenUp. The next data point is then a MoveTo. All data points not preceded by the predetermined special data point are LineTos.
Such a data scheme limits the resolution of the signature to less than the position represented by the predetermined special data. However, where the resolution of the signature pad is less than the predetermined special data point, the SIG format is an effective compression—particularly because LineTo's are many times more frequent that MoveTo's in signature data.
Prior-art signature compression processes reduced the “pixel” resolution of the signature. This reduction destroyed a portion of the data to be captured.
Accordingly, the art evinces a need for a process for electronically capturing and compressing signatures that produces high compression ratios and nonetheless retains all of the original signature information.
These and other goals of the invention will be readily apparent to one of ordinary skill in the art on reading the background above and the description below.
(The drawings are not to scale.)